Aromatic polyketones are known to enjoy good resistance to thermal degradation. Bonner, in U.S. Pat. No. 3,065,205, suggests the Friedel-Crafts catalyzed polymerization of certain reactants to yield polyketones, listing as typical Friedel-Crafts catalysts ferric chloride and boron trifluoride. The reactants proposed fall into two classes, the first consisting of aryl ethers and polynuclear aromatic compounds, a member of which is heated with a member of a second class consisting of aliphatic and aromatic diacyl chlorides. The basic reactions taught by this patent, then, can be summarized as follows: ##STR2## WHERE HBH is a polynuclear aromatic hydrocarbon such as naphthalene, HR-O-RH is an ether such as diphenyl ether, and Cl-A-Cl is a diacyl chloride such as terephthaloyl chloride or phosgene. When phosgene and diphenyl ether are reacted, the resulting polymer will contain the repeating unit ##STR3##
An entirely different approach is taken by Farnham and Johnson in British Pat. No. 1,078,234 (corresponding to U.S. application Ser. No. 295,519, filed July 16, 1963). Here, polyarylene polyethers are produced by reaction of an alkali metal double salt of a dihydric phenol with a dihalo benzenoid compound. The dihydric phenol may contain a keto group -- thus, 4,4'-dihydroxy benzophenone is claimed to give rise to a polyketone (See claim 15 of the British patent).
The same repeating unit is disclosed in British Pat. No. 971,227 to arise from the reaction of diphenyl ether with phosgene, from the polycondensation of diphenyl ether-4-carbonyl chloride, and from the reaction of diphenyl ether with diphenyl ether-4,4'-dicarbonyl chloride.
A number of patents dealing with improved methods of making polyketones have since issued. Thus, for example, processes disclosed in U.S. Pat. Nos. 3,441,538 and 3,442,857 derive advantage by resort to hydrogen fluoride-enhanced boron trifluoride catalysis, a system earlier recognized in Boron Fluoride and its Compounds as Catalysts, etc., Topchiev et al, Pergamon Press (1959) p. 122; J. Org. Chem. 26, 2401 (1961); and I&E Chem. 43, 746 (1951). A further patent dealing with an improved process is British Patent No. 1,086,021. The foregoing are incorporated herein by reference to illuminate the background of this invention.
In my above-mentioned copending applications, Ser. No. 115,824 and Ser. No. 214,465, are described the manner in which melt processable polymers having the phenoxybenzoyl repeating unit may be obtained. Such polymers are eminently suited to insulative coating of conductive articles such as wire and cable. These applications, however, sometimes require performance without substantial alteration of physical properties at temperatures in excess of the melt point or range of the poly(benzophenone ethers) discussed above. It would be advantageous, then, to secure polyketones having significantly greater melting temperatures, which polymers yet share the other desirable properties of previously known polyketone materials.